We propose to investigate: 1) how tumor recurrence following surgical removal of the AC33 tumor in female Lewis Wistar/Mai rats varies with diet, hormones, and 5-fluorouracil (5FU); and 2) whether dietary and/or hormonal manipulation can be used to decrease the toxicity of 5FU to host tissues, thereby increasing the amount that can be given. The toxicity of 5FU to the tumor and the host will be assayed by measuring the rate of protein synthesis in bone marrow, gut, liver, kidney, heart, lung, stomach, muscle, and tumor under the different dietary/hormonal regimens.